User guide

2.9 System Disk
The system unit contains at least one hard disk. You cannot physically access
the hard disk. This hard disk, called the system disk, holds the factory
installed software (FIS). FIS is a VMS™ operating system, which is installed
before the system is shipped. You can use an operating system stored in a
different location if you prefer, but VMS version 5.5-2H4 or later is mandatory.
See the VMS Factory Installed Software User Guide for more information on
using VMS FIS.
2–42 Internal System Devices